1. Field of the Invention
The present invention relates to an optical recording carrier and an optical recording process which can reduce a data access time and increase a data recording capacity.
2. Description of the Related Art
In general, a write-once type optical disk, a magnetooptic disk and a phase-changing type optical disk are practically used as an optical recording medium utilizing an optical recording material.
However, such a general optical recording medium has the following disadvantages.
Namely, the write-once type optical disk can record data, but cannot rewrite data by erasing the recorded data, therefore one disadvantage is that a utilizing range of this optical disk is narrow.
In contrast to this, the magnetooptic disk can rewrite data, but it is necessary to provide a magnetic head for generating an auxiliary magnetic field for recording and erasing data on the magnetooptic disk. Therefore, the cost of a device using the magnetooptic disk as a recording medium is increased. When data are rewritten, it is necessary to erase the recorded data once. This results in increasing a time required for rewriting a data and increasing a data access time. For example, a two-beam system, a magnetic field modulating system, an optical modulating system using an initializing magnet by an exchange coupling multiple layer medium, etc. are practically used as a device capable of performing a data rewriting operation by one disk access using the magnetooptic disk. However, this device has a complicated structure and cost of this device is increased. Further, manufacturing yield of the used recording medium is bad and cost of the recording medium is increased.
In the phase-changing type optical disk, an optical recording material is constructed by a thin phase-changing optical recording film of In-Se-Tl-Co elements, In-Sb-Te elements, Ge-Sb-Se elements, etc. to perform a data rewriting operation by one disk access. However, in the phase-changing type optical recording film, the temperature of a light irradiating portion is set to a temperature equal to or higher than a melting point at a data recording time. Accordingly, it is necessary to set the output level of a laser beam to be very high. Therefore, the life of a semiconductor laser element for outputting the laser beam is short, or a large heating amount of the semiconductor laser element prevents the device interior from being fully cooled. Further, the temperature of the phase-changing type optical recording film at the data recording time is set to a very high temperature such as 400.degree. to 800.degree. C. Accordingly, a protecting layer of the phase-changing type recording film must have characteristics in which no protecting layer is melted and decomposed and it is possible to prevent the recording film from being deformed at the recording time. Therefore, the protecting layer is constructed by a special layer so that the cost of a recording medium is increased.